The reticular formation of the brain stem plays a critical role in producing slow and rapid eye movements and positions of fixation. In this work, we are investigating the nature of this control. In experiments on cats, glass microelectrodes have been used to record intracellular events and field potentials in and around eye muscle motoneurons. Using this technique, pathways from the reticular formation to eye muscle motoneurons are being traced electrophysiologically. In experiments on alert monkeys extracellular unit activity in the brain stem reticular formation and vestibular nuclei are being related to eye movements recorded with electrooculography. Patterns of unit discharges will be correlated with activity predicted by models of the oculomotor system. This research should lead to better understanding of the organization of reticulo-oculomotor connections and of how activity of neurons in the reticular formation might be organized to generate slow and rapid eye movements. Such information is important for understanding the central oculomotor system and should facilitate diagnosis and treatment of patients with disorders of the oculomotor, visual and vestibular systems. BIBLIOGRAPHIC REFERENCES: Henn, V. and Cohen, B. Activity in eye muscle motoneurons and brainstem units during eye movements. In: Basic Mechanisms of Ocular Motility and Their Clinical Manifestations, G. Lennerstrand and P. Bach-y-Rita (Eds.), Pergamon Press: New York, pps. 303-324, 1975. Cohen, B. and Uemura, T. Ocular changes in monkeys after lesions of the superior and medial nuclei and the vestibular nerve roots. In: The Vestibular System, R. Naughton (Ed.), Academic Press: New York, pps. 187-202, 1975.